Process for manufacturing soap



Patented Sept. II, 1951 PROCESS FOR MANUFACTURING SOAP Hans GeorgeKirschenbauer, Allendale, N. .L, and

Joseph Henry Percy, deceased, late of Woodmere, N. Y., by Constance L.Percy, executrix, New York, N. Y., assignors to Colgate-Palmolive-PeetCompany, Jersey City, N. J a corporation of Delaware No Drawing.Application September 9, 1947, Serial No. 773,069

13 Claims. (Cl. 260419) This invention relates in general to themanufeature of soaps, and more particularly to a process for improvingthe color and odor of soap by the removal of undesirable materialsduring manufacture.

Common soap, an alkali metal (usually sodium) salt of fatty acids, ismade by the treatment of fatty esters and/or free fatty acids withalkali. The esters generally used are glyceride type, and arepredominantly combinations formed by the union of a molecule ofglycerine and three molecules of fatty acids. When glyceride oils orother fatty acid esters are heated with alkaline hydroxide, the estermolecule splits, forming glycerinc and soap. Similarly, when fatty acidsare heated with alkaline hydroxide, water and soap are formed.

The soap boiling process, as carried out according to general kettleroom practice in the manufacture of soap from glyceride oils and fats,usually comprises five stages, or changes, as follows:

Killing, in which aqueous alkali is added to molten fat in a kettle, andthe mixture boiled with the aid of open and closed steam coils;

Graining, in which an inorganic alkali metal salt is added to themixture until the soap previously formed is thrown out of solution and,upon settling, forms a top surface layer, the aqueous spent lye phasebeing withdrawn from the bottom of the kettle;

Washing, in which the soap is brought into solution, or closed by theaddition of water of a successive boiling;

F ttin i which wa r is aref ly "a ed to the boiling soap to reduce thesolute concentration so that, upon settling, the lye will dissolve afraction of the soap, the several layers formed, including theundissolved neat soap, the partially dissolved nigre fraction and theremaining lye solution, being drawn oil separately. The nigre fraction,comprising that portion of the soap which has gone back into solu- 7,

tion, usually contains heavy metal soaps, hydrox a s a d o er mpu itieswh h m a a poor color to th fin shed s p odu i o removed.

Af er set lin t e bo led s ap is. usually dr off and agitated in amixing device, called a crutcher, where additional elements areintroduced, such as talc, starch, silicates, coloring, etc. From thisstage the soap may be cooled and worked mechanically, as in the millingprocess, allowed to settle and harden as in the framing process, bespray dried or otherwise treated, perfume added where desired andultimately packed and shipped.

In the milling process, the soap is drawn from the crutcher, cooled andconverted into ribbons by deposition in molten form on chilled rolls,and subsequent scraping therefrom, whence it is dried, mixed in anamalgamator with perfume and other agents, made homogeneous byprocessing on milling rolls, and extruded in bar form from aworm-operated compacting device called a plodder.

Modifications of the boiling process described are known to be widelypracticed with respect to each of the changes. For example, in thekilling change, saponification may be carried out to an extent of fromto almost complete saponification. Occasionally the washing andstrengthening steps are omitted. Fitting may be accomplished by firstclosing the soap completely and thereafter subjecting the solution topartial graining. In still other processes the soap may be subjected toa half-finish, in which Water is added in the mixture containing theundissolved, grained soap, but added only in amounts insufiicient toseparate any nigre. The solution is then withdrawn from the mixture, andthe soap finished by the further addition of Water to separate thenigre.

When soaps are manufactured by the neutralization of substantially purefatty acids, the kettle boiling processes generally used are much thesame as in saponillcation. The fatty acid is mixed with alkalinehydroxide and the mixture grained, settled out and separated.

Washing, which is employed in saponification for removing alcohol formedin the reaction, such as 'glycerine in the saponification of glycerides;is less necessary in neutralization, as the reaction products comp-risemainly water and soap. The soap is usually closed into solution aftergraining by the addition of water to the boiling mixture, strengthenedwith alkali and fitted. The proportion of nigre necessary to beseparated to insure good color in soap resulting from neutralization isgenerally less than that required in soap manufactured bysaponification, which condition seems best accounted for by the priorrefining of free fatty acids which is usually incident to th ei rmanufacture.

The fatty materials and the alkali used in malt.-

ing soaps often contain heavy metals, such as iron, manganese, copperand others. The presence of such metals contributes to poor color andlack of stability in the soap product, and also form heavy metal soaps,that the metals ortheir soaps may catalyze oxidation of the fattymaterials, either during the processing of the soap or 4 ous mass intosolution by the addition of water, and subsequently partially grainingby addition of electrolyte such as lye, salt or a mixture thereof.

. In such a process the phosphate-yielding substances may also be addedbefore, with or after the addition of water.

after the product has been finished and marketed,

that the metals themselves may undergo oxidation, and that these andother deleterious effects may occur, singly or in combination, to causethe soap product to exhibit oor and/or unstable color and odor:

In the past, it has been practice to remove impurities from fattymaterials by subjecting them to a sulfuric or phosphoric acid wash priorto saponification. Washes, as so applied, are conventionally carried outin vessels lined with inert substances, and large or substantialquantities are usually washed at one time. Fatty material, whenacid-washed, generally requires a subsequent water washing to attain thedesired degree of purification and particularly to remove the acid fromthe material. Thus, when fats intended for soap making are pretreated byan acid wash,- undesirable inconvenience and added expense accompany theimprovement in the final product.

Methods other than acid-washing have been used previously also. Some ofthese which comprise incorporating organic antioxidants in the soap soas to prevent oxidation, however, do not provide for removal of theharmful metals. Still other methods have been proposed, comprising theaddition in a reaction mixture of sulphiding materials, such as sodiumthiosulphate so as to incorporate them with the soap and to removeundesirable materials such asmetals therefrome This has thedisadvantage, however, that remnants of sulfur-containing materialscarried 4 in the finished soap have a deleterious eifect upon the odorthereof.

It has now been found that soap of good color, odor and stability can bemanufactured by the conventional soap boiling process by adding in themixture, prior to fitting, a small proportion of a substance capable ofyielding phosphate ions. It is believed that the addition of phosphateions in the mixture causes undesirable metals to formrelativelyinsoluble phosphate salts which, upon settling of the mixture,remain largely in the lower or denser lye or .nigre layer, and arethereby substantially eliminated from the less dense or upper layer offinished soap. This treatment has no deleterious effect on the perfumewhich is later added to the soap.

Phosphates have previously been added to soap and soap mixtures afterthe completion of the ,boiling process, for example, in the crutchingoperation. Their presence per se has not been observed to exert anyharmful effect on the mixture, and in many cases phosphates aredesirable ingredients in soap products.

While fitting is carried out by adding water to partially close aheterogeneous system of undissolved soap and dissolved electrolyte, thephos- .phates may be effectively added before, with or after theaddition of the Water. Similar fiexi- ,bility is afforded where fittingis accomplished by completely closing, or dissolving, a heterogene- Incarrying out the process, for example in the kettle saponification offats, molten fat may be killed and boiled with alkali in an ordinarymanner, grained, washed, strengthened and phosphating material added inan amount of from 0.10 to 5.0% of the weight of the fat. The mixture maythen be boiled further, subjected to fitting and, upon settling, theneat soap drawn off for further processing according to the framing,milling, spray drying or other method of finishing.

The phosphating materials may be added-in the soap mixture while thesoap is in or outof solution, however it is generally desirable thatthey be added after the removal of any solutions which may later betreated for purification of glycerine contained therein. The spent lyeremoved from the mixture after the first graining is generally sotreated, and where the unspent lye of a previous strengthening change isused as a killing lye, these considerations make it somewhat desirablethat the phosphating materials be added after the strengthening change.

In the case of neutralization of fatty acids, more liberty is possiblebecause of absence of the glycerine removal problem. Addition of thephosphating materials, when performed while the soap is in solution,appears to have a quicker action, however not to constitute any greatdifference in the ultimate result of the treatment.

The process of soap making in its manifold variations may be carried outusing the process of the invention herein disclosed. Soaps made bymodified boiling processes, and particularly those already mentioned inwhich steps such as washing and strengthening are omitted, may beimproved in quality and appearance by the use of the present invention.

The process may be carried out in the preferred form by the addition ofphosphoric acid or any of the soluble alkali metal phosphates andpolyphosphates, including sodium orthophosphate,

- sodium monohydrogen orthophosphate, sodium dihydrogen orthophosphate,sodium pyrophosphate, sodium hexametaphosphate, potassiumorthophosphate, potassium monoand dihydrogen orthophosphate, potassiumpyrophosphate, sodium and potassium tripolyphosphates andtetraphosphates, etc., and mixtures thereof.

While substances which yield phosphate ions, other than free phosphoricacid and its soluble alkali metal salts, are operative in the process insome degree, it is preferred to use substances from the classesmentioned, because of the known harmlessness of small proportions ofhydrogen and alkali metal ions in a soap kettle mixture.

The method of the present invention may be employed in any conventionalsoapboiling process, including those wherein soap is made from freefatty acids, fattyglycerides and other fatty acid esters, such as thefatty acid esters of the lower aliphatic monoand polyhydric alcohols.Typical starting materials include coconut oil, palm oil, palm kerneloil, cottonseed oil, tallow, menhaden oil, olive oil, corn oil, tungoil, soya bean oil, whale oil, etc., and the split fatty acids and lowermonoand polyhydric alcohol esters derived from these.

The process of the invention, hereinbefore described :as appliedhip-conventional kettlefind pan-boiling soap manufacture, is not limitedto .these methods and is profitably extendedrinto other techniques ofsoap making, for example the continuous method.

Where'soap is made continuously by progressively intermingling a sourceof fat-and aqueous 'oaustic alkali, and the reaction products are laterseparated mechanically, as in conventional fitting-and-settling orcentrifugation, or by other physical methods, such as flashdistillation, the phosphating materials may be added in the mixture at aconvenient point prior tomsuch separation.

The manner and method of separating the soap from the mixture hasapparently negligible influence upon the reaction of the 'phosphating.materials with any portion of the mixture, however, thoseprocesses inwhich the final mixture is separated by settling, centr-ifugation orotherwise, possess added advantage in regard tothis invention in thatany harmful materials precipitated are removed permanently from theproduct and retained by the aqueouslayer, i. .e., the lye or nigre.

Typical instances of application of the inven- -tion in soap boilingprocesses are described in the following examples, which are included toillustrate but not to limit the invention:

Example I Fatty acids, obtained by hydrolyzing a low grade palm oil, areconverted into soap in a kettle boiling process. After one lye wash,0.25%

of trisodium phosphate (basis free fatty acid) is added to the boilingcurd soap. The kettle contents are next given a half finishingtreatment, then finally finished off by closing to a medium fit, andsettling until Stratification had taken place.

distinctly lighter than those made without the treatment and show, aftertwo months aging, a difference in color which is even more pronounced,and, in addition, a difference in'odor which is in favor of'thephosphate-treated sample.

Exampl II 280 parts by weight of commercial Red 011 are boiled with anaqueoussolution of 55 parts of caustic soda in a soap kettle. The. soapis subjected to one lye wash and divided into two equal portions. Fourparts of trisodium phosphate are added to one portion, while no suchaddition is made to the other. ..A n ere i p rated ro each fra t on byaddin Water n oiling wit open steam. After settling, the neat soaps areseparately crutched with addition of D fume and poured into molds. Uponexamination, the soap which had been treated with the phosphate is foundto have a light color, whilethe untreated soap is quite dark, having areddish brown hue. On aging for three months, the diference in color hasbecome even more pronounced, and the untreated soap-has'a poorer odorthan the treated sample.

40 The neat soap is converted into chips ,by chilling on cooling rollsandby processing in Example III A good grade of tallow, such asis'generally used in the manufacture of toilet soap, is converted intosodium soap in a conventional boiling process. After the customarylye-changes have been made, and the lye fromthe final change, orhalf-finish, has been withdrawn, a proportion of technicalortho-phosphoric acid is added in the .amount of 0.2% of the tallow,together with an amount of water necessary to obtain separation of anigre. After the kettle contents are allowed to settle, the neat soap iswithdrawn and converted into toilet soap by conventional processingincluding cooling on chill rolls, drying, amalgamating, milling,plodding, etc. In the amalgamator 0.75% perfume is incorporated into thesoap. The product of this process. is considerably lighter in color thananother sample prepared in identical manner from the same stock exceptthat nophosphoric acid was added during processing. On aging thedifference in color becomes more pronounced and the original scent isconsiderably better preserved in the sample which had been subjected tothe phosphoric acid treatment.

Example IV I A soap prepared from cottonseed foots is treated, prior tosettling, with .tetrasodium pyrophosphate in the amount of 0.75% of thefat used. The neat soap obtained is converted into powder form by dryingon steam heated rolls and 0.60% ,neri'ume added in an amalgamator. Forcomparative purposes, a second portion of the same stock is prepared ina corresponding manner, except that no phosphate was used. There is astriking difierence in the color of the two prod- .ucts and, on aging,the color and odor of the untreated product becomes progressively worsewhile the treated product showed onlya very moderate darkening and notso pronounced *a change in aroma.

Example V Three samples of sodium soap are prepared from tallow, usingconventional soap-boiling procedure, consisting of killing.-ll'fiwhangirIg and fitting. Prior to settling, trisodium phosphate isadded in one mixture in the amount of 0.25% of the tallow, in another inthe amount-of3% of the tallow, and in the third, no addition ofphosphate is made. On settling, the neat soaps are poured into molds andwhen examined, good color is manifested in the order of most phosphatetreatment, the sample in which 3% phosphate had been used being a verygood color, the 0.25% sample a slightly darker hue, and the untreatedsample the poorest of the three. On aging, at the end of two months, thecolor differences have magnified, the untreated sample being appreciablydarker than previously, and the sample which was treated with 3%phosphate showing the least change.

Example. VI

-' of 1% of the coconut oil is added in the mixture.

'The mixture is closed with water to a medium fit, and after settling,the neat soap is withdrawn, 1% perfume added and poured into molds. Uponcooling, the sample is seen to be of very good color, while anuntreatedsample, made under otherwise identical conditions, is of a darker shade.On aging, the color difference between Example VII .A charge ofcottonseed oil is subjected to a soap boiling process for conversioninto sodium soap. After a final lye-wash has been performed, and the-lyewithdrawn, the mixture is closed completely into solution by theaddition of water with open steam. To the boiling solution is added aproportion of potassium pyrophosphate in the amount of 2% of thecottonseed oil. .The soap is partially grained to a medium lit by theaddition of electrolyte, and permittedto settle. The

neat soap is drawn off, crutched, 1% of perfume added and a samplepreserved in molded form for observation. The sample has good color,while a similar sample, made from the same stock by identical processingexcept for the phosphate treatment, shows a poorer color, whichdifference between the samples is more striking after an aging period oftwo months, in addition to which the untreated sample has lost more ofits odor upon aging.

Example VIII A charge of coconut oil is converted into sodium soap in aconventional soap-boiling process. After a final lye-wash has beenperformed, and the lye withdrawn, tetraphosphate of sodium is added inthe amount of 1% of the coconut oil in the boil, and the resulting massthen closed to a medium .fit. After settling, the neat soap isWithdrawn,

crutched, 1% perfume added and poured into molds. The molded sampleshave good color and stability, while similar samples, made from the samestock by identical treatment except for the addition of phosphate, showa poorer color which becomes increasingly worse with aging.

Example IX The process of Example VIII is carried out using sodiumtripolyphosphate in place of tetraphosphate. The resulting moldedsamples show good color and stability as compared with a control madewithout benefit or phosphate, which deteriorated rapidly upon aging.

- While the description herein is limited to certain specific forms ofthe invention, it should be understood that the invention is limitedonly as defined in the appended claims.

What is claimed is: 1 1. In the making of soap from fatty glycerides bya process which includes a fitting operation in which the soap issettled into layers including neat soap, nigre and lye, the improvementwhich comprises adding to and mixing with the soap,

prior to settling, a water soluble material yielding phosphate ions inthe resulting mixture, settling the soap to form layers, and separatingthe neat soap from the other layers which contain the major portion ofthe phosphate material including impurities removed from said neat soap.1

. 2. The process as set forth in claim 1 in which the soluble materialis phosphoric acid.

3. The process as set forth in claim 1 in which the'soluble material isan alkali metal phosphate salt.

- 4. The process as set forth in claim 1 in which the soluble materialis sodium orthophosphate.

5.'Theprocess which comprises saponifying 'fatty iglycerides withaqueous alkaline saponifier,

phosphate ions in the resulting mixture; and

separating a less dense soap phase from a denser phase containing amajor proportion of the phosphate material including impurities removedfrom said less dense soap phase. e

6. The process as set forth in claim 5 in'which the soluble'material isphosphoric acid. a

'7. The process as set forth in claim 5 in which the soluble material isan alkali metal phosphate salt.

8. The process which comprises saponifying fatty glycerides with aqueousalkali metal hydroxide, graining out the soap and separating the grainedsoap from an aqueous phase, adding to saidseparated grained soap wateran electrolyte including soluble material yielding phosphate ions in theresulting mixture, said Water and electrolyte being added in sufficientamount to effect phase formation, and separating a less dense. soapphase from a denser aqueous phase. 9. The process as set forth in claim'8' in which the soluble material is phosphoric acid. I

10. The process as set forth in claim 8 in which the soluble material isan alkali metal phosphate.

11. The process of making soap of improved color. and stability whichcomprises saponifying fatty glycerides with an alkali metal. saponifier,adding, an inorganicelectrolyte and separating a soap phase from anaqueous phase, adding to said soap phase sufficient aqueous electrolytesolution containing a soluble material yielding phosphate ions'in theresulting mixture to effect phase formation, and separating a less densesoap phase from a denser aqueous phase.

12. The process as set forth in. claim 11 in which the saponifier issodium hydroxide and the soluble material is sodium phosphate.

13. In the process of making sodium soap from fatty-glycerides by thekettle process, the improvement which comprises adding, to the soapafter graining but prior to fitting a minor amount of alkali metalphosphate and separating a less dense soap phase from atdenser aqueousphase containing the major portion of said phosphate combined withimpurities removed from said HANS GEORGE 'KIRSCHENBAUER.

CONSTANCE L. PERCY, I

Executrix of the Last Will and Testament of Joseph Henry Percy,Deceased.

REFERENCES CITED The following references are of ,record in the file ofthis patent!- 1 UNITED STATES PATENTS Number Name a Date 2,383,630 TrentAug. 28, 1945 2,383,631 Trent Aug. 28,1945 2,391,019 Hirsch Dec. '18,1945 FOREIGN PATENTS Number 3 Country Date 1 494,056 Great Britain Oct.19, 1938 OTHER REFERENCES Kirschenbauer: Fats and Oils. (1 944)Reinzhold Pub.Co., pa es 47 and 4s.

1. IN THE MAKING OF SOAP FROM FATTY GLYCERIDES BY A PROCESS WHICHINCLUDES A FITTING OPERATION IN WHICH THE SOAP IS SETTLED INTO LAYERSINCLUDING NEAT SOAP, NIGRE AND LYE, THE IMPROVEMENT WHICH COMPRISESADDING TO AND MIXING WITH THE SOAP, PRIOR TO SETTLING, A WATER SOLUBLEMATERIAL YIELDING PHOSPHATE IONS IN THE RESULTING MIXTURE, SETTLING THESOAP TO FORM LAYERS, AND SEPARATING THE NEAT SOAP FROM THE OTHER LAYERSWHICH CON TAIN THE MAJOR PORTION OF THE PHOSPHATE MATERIAL INCLUDINGIMPURITIES REMOVED FROM SAID NEAT SOAP.